Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon

Definitions

• the present invention relates to copper alloys containing magnesium and phosphorous and which exhibit electrical conductivity of 90% IACS or higher and significantly higher strength properties.
• the strength x conductivity factor of these alloys peaks around 6300 units. However, these alloys are very difficult to produce, suffer from very high variations in properties, and do not exhibit good formability .
• Alloys such as these represent the best combinations of strength and conductivity, in some cases exceeding that of pure copper. These alloys have good formability; however, their resistance to heat is limited. High conductivity alloys are used in applications where they are exposed to high temperatures for short durations. These alloys while capable of retaining a significant part of their strength at 710°F, lose an unacceptable part of their strength when exposed to temperatures such as 800°F, even for a few minutes.
• U.S. Patent No. 4,605,532 to Knorr et al. illustrates an alloy which consists essentially of from about 0.3 to 1.6% by weight iron, with up to one half of the iron content being replaced by nickel, manganese, cobalt, and mixtures thereof, from about 0.01 to about 0.2% by weight magnesium, from about 0.10 to about 0.40% phosphorous, up to about 0.5% by weight tin or antimony and mixtures thereof, and the balance copper.
• the Knorr et al. alloys are based on a high phosphorous to magnesium ratio which is at least 1.5:1 and preferably above 2.5:1. The result of this is that whereas all the magnesium in the Knorr et al.
• the Knorr et al . alloys is likely to be tied up with phosphorous, other elements like iron and cobalt will be left in solution in large amounts. As a consequence, electrical conductivity will suffer.
• the Knorr et al . alloys also contain coarse particles having a size in the range of 1 to 3 microns. As a result, the Knorr et al. alloys will exhibit poorer ductility, formability, resistance to softening, and lower strength x conductivity factors .
• U.S. Patent No. 4, 427,627 to Guerlet et al. relates to a copper alloy essentially comprising 0.10 to 0.50% by weight cobalt, 0.04 to 0.25% by weight phosphorous, and the remainder copper.
• the cobalt and phosphorous additions are made so that the ratio of cobalt to phosphorous is between 2.5:1 and 5:1, preferably 2.5:1 and 3.5:1.
• Nickel and/or iron may be substituted for part of the cobalt; however, the nickel and iron may not be present in an amount greater than 0.15% with nickel being present in an amount less than 0.05% by weight and the iron being present in an amount less than 0.10% by weight.
• the Guerlet et al .
• alloys may contain one or more of the following additions: from 0.01 to 0.35%, preferably 0.01 to 0.15%, by weight magnesium; from 0.01 to 0.70%, preferably 0.01 to 0.25% by weight cadmium; from 0.01 to 0.35%, preferably 0.01 to 0.15% silver; from 0.01 to 0.70, preferably 0.01 to 0.2% by weight zinc; and from 0.01 to 0.25%, preferably 0.01 to 0.1% by weight tin.
• the alloys of this patent suffer from the deficiency that the importance of forming magnesium phosphide and/or iron phosphide particles of particular sizes to improve physical properties such as formability, ductility, and resistance to softening while maintaining high strength properties and electrical conductivity is not recognized.
• U.S. Patent No. 4,750,029 to Futatsuka et al illustrates a copper base lead material for semiconductor devices.
• the material consists essentially of from about 0.05 to 0.25% by weight tin, from 0.01 to 0.2% by weight silver, from 0.025 to 0.1% by weight phosphorous, from 0.05 to 0.2% magnesium, and the balance copper and inevitable impurities.
• the P/Mg ratio is within a range from 0.60 to 0.85 so as to form a compound of magnesium and phosphorous or Mg 3 P 2 . Alloys of this type are typically marked by a low strength x conductivity factor.
• the '337 patent document illustrates a copper alloy containing 0.004 to 0.7% phosphorous, 0.01 to 0.1% magnesium, 0.01 to 0.5% chromium, and the balance copper. Alloys of this type exhibit electrical conductivities in the range of 80 to 90% IACS in an annealed condition; however, the strength x conductivity factors are less than desirable.
• the '439 patent document illustrates a copper alloy containing 2 to 5% iron, 0.2 to 1.0% magnesium, 0.3 to 1.0% phosphorous and the balance copper. Alloys of this type enjoy high strength properties and very low electrical conductivities.
• Japanese patent document 53-19920 relates to a copper alloy containing 0.004 to 0.04% phosphorous, 0.01 to 02.0% of one or more of magnesium, silicon, manganese, arsenic, and zinc, and the balance copper. While alloys within these ranges enjoy electrical conductivities in the range of 80 to 90% IACS, they suffer from low strength properties.
• U.S. Patent No. 2,171,697 to Hensel et al relates to a copper-magnesium-silver alloy.
• the silver is present in an amount from 0.05 to 15%, while the magnesium is present in an amount from 0.05 to 3%.
• Alloy 19720 contains 0.06 to 0.20% magnesium, 0.05 to 0.15% phosphorous, 0.05 to 0.50% iron, and the balance copper.
• the alloy designated 19720 per published data, has an electrical conductivity of 80% IACS in soft condition and a tensile strength of 60 to 70 ksi in hard temper .
• copper-magnesium-phosphorous alloys in accordance with the present invention consist essentially of magnesium in an amount from about 0.01 to about 0.25% by weight, phosphorous in an amount from about 0.01 to about 0.2% by weight, silver in an amount from about 0.001 to about 0.1% by weight, iron in an amount from about 0.01 to about 0.25% by weight, and the balance copper and inevitable impurities.
• the magnesium to phosphorous ratio is greater than 1.0.
• copper-magnesium-phosphorous alloys in accordance with the present invention consist essentially of magnesium in an amount from about 0.01 to about 0.25% by weight, phosphorous in an amount from about 0.01 to about 0.2% by weight, optionally silver in an amount from about 0.001 to about 0.1% by weight, at least one element selected from the group consisting of nickel, cobalt, and mixtures thereof in an amount from about 0.05 to about 0.2% by weight, and the balance copper and inevitable impurities.
• the Figure is a schematic representation of the processing of the copper alloys of the present invention.
• the alloys of the present invention are copper-magnesium- phosphorous alloys. They are characterized by high strength properties, high electrical conductivity, high strength x conductivity factors, improved ductility and formability, and improved resistance to softening.
• the alloys in accordance with the present invention include in a first embodiment those copper base alloys consisting essentially of magnesium in an amount from about 0.01 to about 0.25% by weight, preferably from about 0.07% to about 0.15% by weight, phosphorous in an amount from about 0.01 to about 0.2% by weight, silver in an amount from about 0.001 to about 0.1% by weight, iron in an amount from about 0.01 to about 0.25% by weight, preferably from about 0.01% to about 0.2% by weight, and most preferably from about 0.01% to a maximum amount of about 0.05%, and the balance copper and inevitable impurities.
• These alloys typically have phosphide particles uniformly distributed throughout the alloy matrix, which phosphide particles have a peak size of approximately 0.2 microns. These phosphide particles, while strengthening the alloys, cause no harm to their formability and ductility.
• These alloys may include at least one additional element selected from the group consisting of tin, silicon, and mixtures thereof. This at least one additional element may be included in amounts less than about 0.2% by weight. Typically, when one of these elements is added, it is added in a minimum amount of 0.001% by weight.
• These alloys may also include up to 0.1% by weight of at least one additional element selected from the group consisting of boron, beryllium, calcium, chromium, zirconium, titanium, and mixtures thereof.
• the alloys may include up to about 0.2% of an additional constituent selected from the group consisting of nickel, cobalt and, mixtures thereof.
• Preferred embodiments of the alloys of the present invention include from about 0.05% to about 0.2% of at least one of nickel and cobalt, and most preferably from about 0.11% to about 0.20% of at least one of nickel and cobalt.
• Iron in the aforesaid amounts increases the strength of the alloys and promotes the production of a fine grain structure.
• Nickel and/or cobalt in the aforesaid amounts are desirable additives since they improve strength by refining the grain and forming phosphides. Additionally, they have a positive effect on conductivity.
• phosphorous addition allows the metal to stay deoxidized, making it possible to cast sound metal within the limits set for phosphorous.
• phosphorous forms a phosphide with iron and/or iron and nickel and/or iron and magnesium and/or a combination of these elements which significantly reduces the loss in electrical conductivity that would result if these materials were entirely in solid solution in the matrix.
• 0.01% phosphorous in solid solution would decrease the electrical conductivity by 8% IACS.
• iron in solution would decrease the electrical conductivity by another 5.5% IACS.
• minimal amounts of iron and minimal amounts of phosphorous must be present in solution.
• magnesium is added to the alloys in the aforesaid ranges.
• the magnesium is further added so that the Mg:P ratio is at least 1.0 and preferably greater than 1.0.
• the composition of alloying elements is selected so that the elements in order of effect on conductivity, P, Fe, Co (where added) are present to the maximum extent as phosphides with none or a minimal amount of them in solution.
• Magnesium on the other hand, which causes minimal drop in electrical conductivity when left in solution, is added in a proportion which causes some residual amount of magnesium to be left in solution. This residual magnesium ensures that any phosphorous that is not tied up with elements like iron, cobalt and nickel, will be tied up by the magnesium (form magnesium phosphide particles).
• alloys formed in accordance with the present invention have negligible iron and only about 0.0036% by weight phosphorous (about 5% of the phosphorous added to the alloy) in solution. Still further, the alloys have approximately 0.035% by weight magnesium in solution. In comparison, a magnesium-phosphorus-silver-copper alloy containing 0.108% magnesium, 0.068% phosphorous, and 0.04% silver and the balance copper and inevitable impurities has approximately 0.0067% phosphorous (approximately 10% of the phosphorous addition) and approximately 0.037% magnesium in solution, resulting in a lower electrical conductivity.
• the alloys of the present invention are optimally thermally treated to form magnesium phosphide particles in the range of about 500 - about 2000 Angstroms and iron phosphide particles in two ranges, a coarse range having particles whose size is in the range of from about 1000 - about 2000 Angstroms and a finer range having particles whose size is in the range of from about 250 to about 600 Angstroms.
• the magnesium phosphide particles and said iron phosphide particles are uniformly distributed throughout the alloy matrix.
• the ratio of coarse iron phosphide particles to fine iron phosphide particles is from about 1:3 to about 1:6.
• the presence of fine iron phosphide particles with the aforesaid size and distribution provide the alloys of the present invention with better ductility and formability. They also provide better resistance to softening since the finer particles allow one to have more particles for the same amount of alloying elements.
• Alloys formed in accordance with the present invention in a cold worked condition, exhibit a strength in excess of 80 ksi with an electrical conductivity of 90% IACS.
• the electrical conductivity of the alloys of the present invention when in soft temper, can reach over 95% IACS.
• Alloys in accordance with the present invention may be processed as shown in the Figure.
• the alloys may be cast using any suitable continuous or non-continuous casting technique known in the art.
• the alloys could be cast using horizontal casting techniques, direct-chill casting techniques, vertical casting techniques, and the like.
• After casting the alloys may be hot worked at a temperature in the range of about 1200°F to about 1600°F to a desired gauge.
• the hot working may comprise any suitable technique known in the art including but not limited to hot rolling. Typical gauges for the material after hot working are in the range of from about 0.400 inches to about 0.600 inches.
• the alloys may be quenched, if needed, and homogenized, if needed, at a temperature of from about 1200°F to about 1600°F for at least one hour. Thereafter, they may be milled to remove material from 0.020 inches to about 0.050 inches per side. Any quenching, homogenizing, and milling may be carried out using any suitable equipment and technique known in the art.
• the alloys of the present invention may be subjected to cold working, such as cold rolling from the milled to finish gauge, with at least one annealing operation in the temperature range of about 700°F to about 1200°F for a time ranging from 1 to 20 hours, until the alloys are in a desired temper.
• Each anneal may include slow cooling with a cooling rate of 20 to 200°F per hour.
• the alloys may be stress relief annealed at temperatures between about 300 and about 750°F for at least one hour.
• this step may be omitted if not needed.
• Illustrative examples of alloys in accordance with this first embodiment of the present invention include: (1) a copper base alloy consisting essentially of about 0.01 to about 0.25% by weight magnesium, about 0.01 to about 0.2% by weight phosphorous, about 0.001 to about 0.1% by weight silver, about 0.01 to about 0.25% by weight iron, up to 0.2% by weight of at least one of nickel and/or cobalt, up to about 0.2% by weight of a first addition selected from the group consisting of tin, silicon, and mixtures thereof, up to about 0.1% by weight of a second addition selected from the group consisting of calcium, boron, beryllium, zirconium, chromium, titanium, and mixtures thereof, and the balance copper and inevitable impurities; (2) a copper base alloy consisting essentially of about 0.01 to about 0.25% by weight magnesium, about 0.01 to about 0.2% by weight phosphorous, about 0.001 to less than about 0.05% by weight silver, about 0.01 to about 0.05% by weight iron, from about 0.0
• a first alloy in accordance with the present invention designated alloy A, containing 0.0807% magnesium, 0.0668% phosphorous, 0.0014% silver, 0.1121% iron and the balance copper and inevitable impurities was cast.
• the coils of the two alloys were cold rolled to 0.080" and annealed at 900°F for a soak time of 7.5 hours; cold rolled to 0.040" and annealed at 850°F for a soak time of 11 hours; and then cold rolled to gauges ranging from 0.0315" to 0.010".
• the tensile strength of the alloy of the present invention is consistently higher than the other alloy at each temperature. The differences are especially significant in view of the alloys being very lean with conductivity approaching pure copper.
• the electrical conductivity of the alloy of the present invention is consistently higher at similar reduction and temper.
• the strength conductivity factor for each temper is significantly higher for the alloy of the present invention.
• the average for the alloy of the present invention is approximately 7% higher than that for the other alloy. This is especially significant since the other alloy already represents the peak of strength and conductivity for existing high conductivity copper alloys.
• EXAMPLE II An alloy in accordance with the present invention having the composition set forth in Example I was taken at 0.160" soft, rolled to 0.030", annealed at 900°F for 10 hours, and then rolled to 0.003" gauge. The alloy so processed demonstrated a tensile strength of 82.65 ksi, an elongation of 3.0%, an electrical conductivity of 90.15% IACS, and a strength x conductivity factor of 7,451. This represents approximately 24% improvement in strength x conductivity combination for pure copper and approximately 16.5% improvement over the best currently available alloys.
• EXAMPLE III Although lean copper alloys have a good combination of strength and conductivity, one area in which these alloys have a problem is in resistance to softening at elevated temperatures. In many applications, the parts are exposed to relatively high temperature for short duration of the order of a few minutes. The strength remaining after this exposure to heat is very important in these applications.
• alloy A had twice as many magnesium phosphide particles as alloy B. Further, the number of iron phosphide particles in alloy A were double the number of magnesium phosphide particles.
• an alloy in accordance with the present invention is a copper base alloy which consists essentially of magnesium in an amount from about 0.005 to about 0.25% by weight, phosphorous in an amount from about 0.005 to about 0.2% by weight, at least one element selected from the group consisting of nickel, cobalt, and mixtures thereof in an amount from about 0.05 to about 0.2% by weight, preferably in an amount from about 0.11% to about 0.20% by weight, and the balance copper and inevitable impurities.
• These alloys typically have phosphide particles uniformly distributed throughout the alloy matrix, which phosphide particles have a peak size of about 0.2 microns. These phosphide particles, while strengthening the alloys, cause no harm to their formability and ductility.
• silver in an amount from about 0.001 to about 0.1% by weight can be added to the alloy.
• These alloys may include at least one additional element selected from the group consisting of tin, silicon, and mixtures thereof. This at least one additional element may be included in amounts less than about 0.2% by weight. Typically, when one of these elements is added, it is added in a minimum amount of about 0.001% by weight.
• These alloys may also include up to about 0.1% by weight of at least one additional element selected from the group consisting of boron, beryllium, calcium, zirconium, chromium, titanium, and mixtures thereof.
• iron in an amount from about 0.01% to about 0.05% by weight can be added to these alloys to improve their strength.
• Nickel and/or cobalt in the aforesaid amounts are desirable additives since they improve strength by refining the grain. Additionally, they have a positive effect on conductivity.
• cobalt it is preferred that it be added in an amount so that the Co:P ratio is between about 4:1 and about 6:1.
• phosphorous forms a phosphide with nickel and magnesium and/or cobalt and magnesium and/or a combination of these elements which significantly reduces the loss m electrical conductivity that would result if these materials were entirely m solid solution m the matrix.
• phosphorous in solid solution would decrease the electrical conductivity by 8% IACS.
• cobalt m solution would decrease the electrical conductivity by another 4.0% IACS.
• nickel in solution would decrease the electrical conductivity by another 1.0% IACS.
• minimal amounts of phosphorous and the other alloying elements must be present m solution.
• magnesium is added to the alloys n the aforesaid ranges.
• the magnesium is further added so that the Mg : P ratio is greater than 1.0.
• the composition of alloying elements is selected so that the elements in order of effect on conductivity, P, Co and/or Ni (where added) are present to the maximum extent as phosphides with none or a minimal amount of them in solution.
• the alloys of the present invention are thermally treated to form magnesium phosphide particles in the range of about 500 - about 2000 Angstroms.
• the magnesium phosphide particles are uniformly distributed throughout the alloy matrix.
• Alloys formed in accordance with the present invention in a cold worked condition exhibit a strength in excess of 80 ksi with an electrical conductivity of 90% IACS.
• the electrical conductivity of the alloys of the present invention when in soft temper, can reach over 95% IACS.
• Alloys in accordance with the present invention may be processed as shown m the Figure.
• the alloys may be cast using any suitable continuous or non-continuous casting technique known in the art.
• the alloy could be cast using horizontal casting techniques, direct-chill casting techniques, vertical casting techniques, and the like.
• the alloys may be hot worked at a temperature in the range of about 1200°F to about 1600°F to a desired gauge.
• the hot working may comprise any suitable technique known in the art including but not limited to hot rolling. Typical gauges for the material after hot working are in the range of from about 0.400 inches to about 0.600 inches.
• the alloys may be quenched, if needed, and homogenized, if needed, at a temperature of from about 1200°F to about 1600°F for at least one hour. Thereafter, they may be milled to remove material from 0.020 inches to about 0.050 inches per side. Any quenching, homogenizing, and milling may be carried out using any suitable equipment and technique known in the art .
• the alloys of the present invention may be subjected to cold working, such as cold rolling from the milled to finish gauge, with at least one annealing operation in the temperature range of about 700°F to about 1200°F for a time ranging from 1 to 20 hours, until the alloys are in a desired temper.
• Each anneal may include slow cooling with a cooling rate of 20 to 200°F per hour.
• the alloys may be stress relief annealed at temperatures between about 300 and about 750°F for at least one hour.

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